For humans, the ability to recall environmental features and past events underlies thinking, planning, and communication, but there are almost no data on recall capabilities in nonverbal animals. Data on the upper limits of recall capabilities in chimpanzees, and on the factors that limit recall, will lead to a more detailed understanding of the similarities and differences between human and nonhuman memory systems to improved animal models of recall memory. The long-term objective of this project is to characterize recall memory capabilities of chimpanzees that underlie communication about the environment and that contribute to the solution of foraging problems. Specific Aim 1 is to assess chimpanzees'recall memory of multiple features of an event. Hypothesis 1: Chimpanzees are capable of episodic memory, as evidenced by their ability to recall and communicate what they saw, where they saw it, who was involved, and features of any objects employed. Specific Aim 2 is to determine which of these different types of information a chimpanzee can recall and convey about a past event at a single reporting session. Hypothesis 2: Chimpanzees can convey multiple features (dimensions) of a past event in a fairly detailed report during a single trial. Specific Aim 3 is to characterize chimpanzees'recall and representational memory of large-scale space. Hypothesis 3: Chimpanzees are capable of recalling and communicating the types and locations of objects in large-scale space, as indicated by: a) their ability to use an artificial language (lexigrams) to learn where distant goal objects are located, and b) their ability to use lexigrams to report the locations of goal objects that are in areas that are completely out of view. Specific Aim 4 is to characterize chimpanzees'ability to recall, rank order, and sequentially visit multiple food resources over a wide spatial area. Hypothesis 4: Chimpanzees rank-order the expected value of multiple distant resources based on quality, quantity, proximity, visibility, and time of occurrence, and then visit the resources sequentially according to their ranking. The research will increase scientific knowledge of basic memory and planning capabilities in primates. Public health benefits of the research are expected to include improved technologies and methods for studying and enhancing memory, planning, communication, and spatial orientation skills in normal and developmentally delayed children.